Each season consisted of 12 to 14 one-hour episodes that focused on historical events or subjects considered to be mysterious by the general public.
Episodes typically begin with Kent giving a broad overview of the subject followed by what is commonly accepted as explanation.
Before commercial breaks, Kent would give the audience bits of trivia relating to the subject; episodes also included a timeline which would give important events occurring around the time of the events discussed in the show.
Subjects covered on the show ranged from the beginning of human history to modern subjects such as Carlos the Jackal, The Amityville Horror, and Area 51, as well as political conspiracies and conspiracy theories such as MK ULTRA and the JFK Assassination.
Common aspects of history covered on the show include religion, crime, the supernatural, archaeology, mythology, and folklore.